This present invention concerns the area of spinal implants in general and in particular osteosynthesis devices, vertebral support devices, and transverse spinal linking devices. Transverse spinal linking devices provide a transverse spacing link between two spinal osteosynthesis bars stabilizing the vertebral column and/or correcting deformations of the vertebral column. Various embodiments of the present invention provide a device that links at least one spinal osteosynthesis bar and a transverse bar. The spinal osteosynthesis bars are intended to adapt to the physiological or pathological curvatures of the vertebral column, and to stabilize the latter and/or correct its curvature defects. These spinal osteosynthesis bars are fixed along the vertebral column by means of bony anchoring resources such as pedicle screws or any other type of fixing means. Often, to facilitate correct retention of the osteosynthesis bars and to allow a good reduction and/or a good setting action, these spinal osteosynthesis bars are connected to each other at one or more points by means of transverse bars. This transverse spacing enhances the stability of the fitting and/or corrective effect (in distraction or in compression).
One problem in the area of transverse spinal linking devices concerns the fitting of these devices to fix the transverse bar to the spinal osteosynthesis bars. In fact, the osteosynthesis bars are fixed along the vertebral column, and the bulk on either side of these bars renders difficult the implantation of the transverse bars and of the transverse spinal linking devices. In fact, the implantation of the transverse spinal linking devices is often difficult because of their small size, and of their structure, which is often complicated to assemble and to mount on the osteosynthesis bars, and because of the frequent necessity to clear the surroundings of the osteosynthesis bar (possibly with an avivement or stripping of the articular processes or a resection of vertebral material).
From previous designs, in particular from patent application WO 03/068087A1 or from patent EP 0793947B1, one is familiar with transverse spinal linking devices with reduced bulk that can be installed on the osteosynthesis bar from the top (by a posterior approach in relation to the vertebral column). These devices of previous design can be mounted on osteosynthesis bars posterior to the vertebral column, using a posterior approach, and allow fixing onto the bar possibly without touching the anterior face of the bar (the side facing the vertebral column). These devices are composed of two jaws that are hinged on an axis located either between the two jaws or off-centre on one of the jaws (which is then fixed). These two jaws are used to grip the bar and to fix the device, which includes a head with a conduit perpendicular to the axis of the spinal osteosynthesis bar. A clamping resource may project into this conduit and to fix the transverse bar while also inducing the closure of the jaws. This closure of the jaws during the clamping of the bar by the clamping resource is achieved by means of the fact that the bar presses onto an edge of at least one of the jaws. These devices have the drawbacks, firstly, of being expensive and relatively complex, requiring an assembly that is complicated and sometimes not very stable, and secondly that the bar is locked between an edge of at least one of the jaws and the clamping resource, which may impose large stresses on the bar and embrittle the bar. These devices have another drawback due to the fact that the jaws tend to close spontaneously even when the clamping resource do not press the bar onto the edge of one of the jaws, which renders difficult the implantation of the devices on the osteosynthesis bar. These devices sometimes correct the latter drawback by means of the presence of stop elements that limit the closure of the two jaws, but this solution adds an extra element, and therefore increases the complexity of these devices.
In this context, it is useful to propose a transverse spinal linking device having a simpler design and a structure configured to ameliorate one or more of the problems presented above, which may allow a fixing of the bar without making the latter fragile, and whose jaws do not tend to close completely before the insertion of the devices on the osteosynthesis bar.